Javascript: recursion + for loop + scope

Question

For the past few days I have tried to solve this problem, but up until now I have not been able to find a solution.

The code below recursively finds paths on a graph. Instead of outputting nodePath's with four nodes, it seems to output 'one nodePath' with a newly added node from every cycle (resulting in path's from 1 to 200+ nodes incrementally). The recursive path call does not seem to make a fresh 'nodePath', however it does with neighbors[node_nw] and depth.

var startNode = s.graph.nodes('n0');
var emptyNodeRoute = [];
path(startNode, 0, emptyNodeRoute);

function path (node, depth, nodePath) {
  nodePath.push(node);
  if (depth == 3) {
    printPath (nodePath);
  } else {
    depth ++;
    var neighbors = s.graph.neighbors(node.id);
    for (var node_nw in neighbors) {
      (function() {   
        path (neighbors[node_nw], depth, nodePath);
      }());
    }
  }
}

//prints node route
function printPath (nodePath) {
  var str = '';
  for(var k = 0; k < nodePath.length;  k++) {
    str = str.concat(' ', nodePath[k].label);
  }
  console.log ('nodePath: ' + str);
}

I guess it has to do with the specificity's of javascript regarding (no) block scoping, closures and recursion? Or maybe something small I am overlooking? I have referenced several resources (amongst http://zef.me/2843/javascript-the-scope-pitfall ) and topics on this site but none of them got me into solving this problem.

Any help would be greatly appreciated!

Answer 1

This is not an scoping, closure or recursion problem, but a reference problem .

You always call the path function with the same nodePath reference. Copy the nodePath variable and everything works as expected.

Here is what you have to change:

for (var node_nw in neighbors) {
   // the method slice makes a copy of the array
   path (neighbors[node_nw], depth, nodePath.slice());
}

Have a look at the working jsFiddle demo .